1. Field of the Invention
This invention relates to copying machines and printing machines, and, more particularly to copying systems or printing systems with a document stacking apparatus and method.
2. Prior Art
Many different output sections for electrostatographic copying systems or printing systems are known in the art for stacked document sets having fasteners. For example, U.S. Pat. No. 5,609,333 discloses a sheet stacking height control system used in a sheet stacking apparatus for stacking plural sheets into at least one stacking tray. Another example, U.S. Pat. No. 5,026,034 discloses an apparatus for feeding and stacking sets of finished sheets in an electrostatographic copier or printer including an anti-dishevelment device for preventing the tearing, dishevelment and other damaging of the top sheet of the top set of the sets in the stack by contacting and holding down such top sheet during the feeding of a new set onto the top of the stack. Both of the above referenced patents are incorporated by reference in their entirety. Document output devices commonly stack fastened, stapled or otherwise finished sets of document sheets one at a time on top of others for later removal by an operator.
A common problem associated with the stacking of document sets is bin or tray under utilization due to stack height variations and the resultant tray or bin capacity variations. The actual and maximum stacking height in a tray or bin can vary considerably with different print job factors. For example, with variations in the sheet thickness, humidity, sheet curl, staples or other binding, edge climbing by sheet edges partially hanging up on vertical registration edges, and other factors affecting stack height. Additionally, maximum stack height may occur only in certain areas of the stack. This is demonstrated especially when fasteners or staples are used in the document set. Stacks of plural fastened or stapled sets tend to have a much higher height level where the fasteners or staples overlie or overlap on top of one another in the stack. Fastener or staple buildup is particularly pronounced for small sets of only a few sheets per stapled set. It has been found for example that a stack of multiple sets of only two sheets per stapled set, such as a common two page letter, can have a maximum stack height in the area of the stack where all those staples overlie one another of more than twice the stack height of other areas of that stack. Consequences of bin or tray under-utilization can include unnecessarily splitting up final print jobs for a user by redirecting them to another mailbox bin or an overflow tray when there was actually still enough stacking room or headspace in the first bin to finish stacking that job or jobs in the first bin. Increased bin or output tray capacity can help to better maximize bin and tray usage and availability when more sheet or document set stacking room is actually available in a given bin or tray. Increased bin or output tray capacity can help to increase productivity and maximizes utilization of the printer output and mailbox system by reducing printing stoppages of the reproduction apparatus, and/or reducing the required number of mailbox bins or output trays. There is a desire to provide a stacking apparatus that provides additional stack capacity to reduce bin or tray under utilization due to stack height variations and particularly stack height variations due to fastener or staple buildup.
Another common problem associated with the stacking of document sets is the tendency of the set being fed and stacked to tear or otherwise damage the top sheet of the top set of the sets already in the stack. This problem is further complicated by limitations with respect to which edge or corner of the document sheets are, for example, fastened, stapled or bound for forming the set. There is a desire to provide a stacking apparatus that provides a reduced tendency of the set being fed and stacked to be torn or otherwise damaged by the sets already in the stack or of the set being fed and stacked to tear or otherwise damage the top sheet of the top set of the sets already in the stack or to be torn or otherwise damaged by the sets already in the stack.
In accordance with one embodiment of the present invention, a document set stacking apparatus is provided for use in a document creating apparatus. A set stacking area is provided that has been adapted to accept a stack of document sets having fasteners. A set relief area is provided which a portion of at least one of the document sets containing the fasteners can be attracted toward by a fastener attractor. In one embodiment, the fastener attractor can be at least one magnet provided adjacent to the set relief area. The magnet attracts the fasteners and the portions of the document sets containing the fasteners toward and into the set relief area.
In accordance with another embodiment of the present invention, a document set stacking apparatus is provided for use in a document creating apparatus. A tray is provided onto which a plurality of document sets having fasteners can be placed. A magnetic device is provided adjacent to the tray and adapted to attract the fasteners. The fasteners are attracted to the magnetic device. As a result, the documents sets are, at least partially, retained in the stack when a new document set is fed on the stack.
In accordance with another embodiment of the present invention, a method of stacking one or more document sets having fasteners on a stacking surface is provided comprising a first step of placing at least one document set on the stacking surface. The fasteners and consequently the region of the set containing the fastener are attracted toward a relief area of the stacking surface by an attracting force.